Change speed device



June 5, 1945 J. M. KENWORTHY CHANGE SPEED DEVICE Filed Ag. 14, 1943 2 Sheets-Sheet 1 torney .ll-lne 5, 1945. 1 M. KENWORTHY 2,377,697

CHANGE SPEED DEVICE Filed Aug. ,14, 1943 2 Sheets-Sheet 2 Patented June 5, 1945 John Melville Kenworthy, Gainsborough, Eng-` land, assignor to Edward Vernon Newey, `Castle Donington, England, and Edward Max Blume, London, England Application August 14, 1943, serial No. 498,6v7 In Great Britain October 23, 1942 3 Claims. (Cl. M -242.4)

is desired to impart to the tool different speeds of rotation.

An `object of the invention is to provide a change speed device, particularly a change speed device suitable for use on machine tools, which is comparatively cheap to produce, can be `built as a unitary structure and` applied to different machines and is simple and eiicacious in use, the device may'alternatively constitute an integral part cfa machine. 1

With the above and other objects in view the invention provides a change-speed device of the type comprising two grooved stepped pulleys mounted in an opposite sense, an` endless belt running in the grooves to transmit the drive from one pulley to the other, passageways on each pulley leading in` opposite directions between successive grooves, and a belt shifter for shifting the belt, throughthe passageways, between successive` steps on the pulley, which belt shifter is provided with rotatably mounted members for engaging the belt while being shifted from one `step to the nextywhich movement would otherwise `be obstructed by the flange that necessarily lies between the two diameters of the pulley, If each pulley has more than two steps, it is preferred that a passageway shall be provided be-` tween each step and the next.

Since it is` necessary that the belt shall be ca-` pable of being shifted in either direction between any two successive steps (i. e. in increasing and decreasing the gear ratio) it is desirable that there shall be two passageways leadingin opposite directions between successive steps, one for conducting the belt from the` smaller to the larger diameter andthe other for conducting it in the reverse direction.

The invention also includes a stepped grooved` pulley with a belt passageway between each or selected ofthe steps.

The foregoing and other features of the invention set out in the appended claims are `incorporated in the construction which will now be described, as an` example, with reference to the accompanying drawings, in which Figure l isa sectional plan of a unit according to this invention; l

Figure 2 is a side elevation and Figure 3 a front elevation thereof;

Figure 4 is a` perspective View of a stepped pulchange-speed ley according to this invention, andFigure 5 is a cross section, partly broken away, thereof.

l Ofn each of two parallelly disposedshafts, I0, II the shaft IIJ Ibeing the driving shaft which is itself rotated from any convenient source of power (such as the electric motor I2) and the other II, being the driven shaft, isdisposed a l stepped grooved pulley; that is to say the pulleys I3, I4 are providedwith a series of grooves I3a, I3b etc. and I 4a, I4b etc. of graduated diameter. The pulleys I3, I4` are aligned and are disposed in an opposite sense; that is to say the step of greatest diameter of one pulley is in line with the step of smallest diameter of the other pulley, the `step of smallest, diameter of the rst pulley is in line with the step of greatest` diameter of the second pulley and the intermediate steps of each pulley are similarly disposed with respect toV one anotherrl The pulleys I3, I4 may be identical with one another. Inthe upstanding ange sep'- applied to a belt I5 riding betweenthe flanges of a stepthe belt follows the belt way in each pulley and moves to thenext higher stepV on one pulley and the nextlower step` on the' otherpulley. When the belt I5 is on theend steps of the pulleys lthe side thrust will ofcourse only be applied to the belt in a direction towards the middle` of the pulley; when the belt is on any of the intermediate steps the thrust may be applied 1n etherdirection. For this reason each of the intermediate flanges are cut withtwo passageways leading in opposite directions, those leading in one direction being lettered.a,yb,\c etc. and those in the other direction being lettered A, B, vC etc,-

The two passageways in eachflange `are spaced apart, Aand the two kinds` of passageways alternate along the pulley as clearly shown in Fig. l. The belt is of truncated Vshape in section withthe widest part outermost. In this unit, as in all mechanisms ofthe grooved pulley and `V-belt type, the belt should not be per#` mitted4 to bottom on the pulley passageways ingly. l l l l,

Disposed between thetwo parallel shafts Ill, I I is a belt shifting device.

are arrangedand disposed accordgrooves. and the l `In the embodiment unbetween the cheeks over of said short shaft I8 are connected by springs 2l to a fixed part of the belt shifting unit and said springs urge the pulley mounted on said short shaft outwardly to tension the belt I5. Said pulley I6 is a grooved pulley and is adapted to accommodate the belt I in its passage from one stepped pulley to the 2| urge such pulleyinto engagement with the belt and take up any slack in the belt; due to the fact that said short shaft I8 is slidable in saidslots I9 it will be appreciated that the effective length of the belt between Ythe'stepped pulleys can in effect be varied. The said side cheeks 29 are of rectangular configuration with their long edges substantially parallel with the direction of the belt between, the stepped `pulleys and the slots I9 in the cheeks lie at right angles to said long sides. The distance between said cheeks is slightly in excess of the pulley mounted on said short shaft and the cheeks are mounted as a unitary structure (being preferably connected by a strap) on a base 2Ia to slide on-a fixed 'base plate 22. The base plate 22 is cut with an inclined slot 23 the angle of which conforms to the cone angle of the pulleys I3, I4, as will be seenv from Fig. l. In this slot 23 a slide I1 attached to the base Zia travels. The said slide II is actuated by a conveniently disposed handle 24 which may if desired be movable relatively to a graduated quadrant to indicate different speed ratios.

The belt passes over one stepped pulley, then between the said cheeks 20 and over the spring urged pulley I6 to the other stepped pulley and on its return to the rst stepped pulley passes the face of the base 2id. At each of the four corners of the cheeks where the belt I5 enters or leaves the cheeks a pair of guide rollers 25 isprovided. The rollers of each pair are displaced fromone another a distance greater than or substantially equal to the width of the beltvand the axes of the rollers are substantially at right angles to the general direction of the belt. That is to say each lap of the belt travels between two pairs of rollers 25. The rollers of each pair are mounted on and fixed to the cheeks 20.

The belt shifter handle 24 is pivoted to the base plate 22 at 2E and is connected to the slide I'I by a screw 21 surrounded by a compression spring 28 that forces the handle 24 downwards so that the latter tends to engage in the recesses 29 of a gate or slot '30 provided at the front of the gear unit. VAn appropriate number of recesses 29 is provided corresponding to the number of steps in the pulleys and the number of gear ratios afforded thereby. In the illustrated example there are six. A device is provided for locating the handle 24 in the appropriate recess. This device comprises a slider 3l movable in guides 32 along the length of the slot 30 and provided with detent mechanism comprising springV pressed balls or plungers 33 co-operating with holes 34 appropriate to each position of the handle 24. vided with a slot 35 for other and the said springs the handle 24, said slotV having a recess 35 midway in the length of its lower edge, which recess 35' is adapted to be aligned with any selected recess 29. When changing speed the handle 24 is first raised against the action of spring 28 clear of the recess 35 and that recess 29 of the gate with which it registers. The handleis then moved'to the right or left until it comes to the end of the slot 35 in the slider 3l. Thereafter the slider 3l is moved with the handle so that the spring pressed plungers 33 disengage from one pair of holes 34 and then engage with the next pair of holes 34. The handle24 is now beyond that recess 29 into which it should drop. This movement of the handle moves the pulley I6 and the latter moves thebelt I5, and as each stepped pulley vreaches the position in which the belt Way in its flanges coincides with the position of the belt the belt The slider 3l is prorides from its first step on each pulley through the belt way on to the next adjacent step, rising up the step on one pulley and falling a similar amount on to the next step of the other pulley. The fact that the short shaft I8 carrying-the pulley I6 of the belt shifter is spring mounted allows for the momentary increase in the effective length of the belt between the stepped pulleys during the change to be accommodated, and the rollers 35 prevent the belt from riding out of the pulley of the shift belt device in that they continue to guide ythe beltxvvhilst permitting change of direction thereof relatively to such pulley; The aforesaid excessive movement of handle' 24 is necessary in order to move the beltI5 from one step to the other successfullyy and quickly,`

but immediately the change has been made the lever 24 is moved in the reverse direction so that itengages in therecess 35 in the slider 3| and in the appropriate recess 29 aligned therewith.

In the illustrated example a second changespeed device is provided soY that the number of gear ratios afforded byv the pulleys I3, I4 is doubled. The motor i2 drives the shaft I0`which drives the driven shaft II as before described; The driven pulley I4 is, however, freely mounted on said shaft I I and has a' V pulley 39 connected to it. The latter drives a countershaft 40 through a /belt 4I and pulley 42 and the countershaft drives another pulley 43, which is free on the shaft il, through pulley 44 and belt 45. 'Ihis pulley system 39, `42, 44, 43 affords a speed change (as illustrated, a speed reduction) as between pulleys I4 and 43. clutched to the driven shaft I'I by'a double cone clutch 46 operated by handle 41. The shaft II may be provided with a power take-off pulley 48.

The change speed device is constructed as uni'-` tary structure, the base 22 being provided with vertical side members 49 between which the shafts are mounted and which support the motor I2v by means of a bracket 5U. The tensionof the belts may be adjusted by adjusting the shafts I0 and 4l). For this purpose the said shafts are supported at their ends in bearing members 5IV that are adjustably secured to` the side plates 49 by means of bolts 52 extending throughk slots 53 in said side plates..Y f

The aforesaid spring pressed pulley I6 is shown in the drawings bearing on the upper lap of the Either of these pulleys may be l pulley, which belt shifter comprises a grooved pulley engaging the belt between the stepped pulleys, and spring means biasinglit against a lap of the belt. l

2. A change-speed device, comprising two stepped, grooved pulleys; means `mounting them .in opposite senses; an endless belt running in the grooves totransmit the drive from one pulley to the other; passageways on the pulleys lead-` grooves; and a belt shifter for shifting thebelt,

through the passageways, between successive steps on the pulley, which beltshifter comprises a grooved pulley engaging the belt between the stepped pulleys, and a pair of spaced rollers between which the belt passes to the grooved shifter pulley and another pair of spaced rolleirsbetween which the belt passesafter leaving saidlshifter pulley, which rollers function to 'apply lateral thrust to the belt when being shifted.

3. A change-speed device according to claim 2 in which the axes of the rollers are substantially ing in opposite directions between successive parallel and are substantially normal to `the axis of the grooved pulley.

JOHN` MELVILLE KENWORTHY. 

